EP0555334B1 - Dryer apparatus - Google Patents
Dryer apparatus Download PDFInfo
- Publication number
- EP0555334B1 EP0555334B1 EP91920008A EP91920008A EP0555334B1 EP 0555334 B1 EP0555334 B1 EP 0555334B1 EP 91920008 A EP91920008 A EP 91920008A EP 91920008 A EP91920008 A EP 91920008A EP 0555334 B1 EP0555334 B1 EP 0555334B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- web
- felt
- dryer
- roll
- disposed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000001035 drying Methods 0.000 claims abstract description 33
- 230000000694 effects Effects 0.000 claims description 5
- 239000012530 fluid Substances 0.000 claims description 3
- 238000011144 upstream manufacturing Methods 0.000 claims 1
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 239000004744 fabric Substances 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000010981 drying operation Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
Images
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F5/00—Dryer section of machines for making continuous webs of paper
- D21F5/02—Drying on cylinders
- D21F5/04—Drying on cylinders on two or more drying cylinders
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F5/00—Dryer section of machines for making continuous webs of paper
- D21F5/02—Drying on cylinders
- D21F5/04—Drying on cylinders on two or more drying cylinders
- D21F5/042—Drying on cylinders on two or more drying cylinders in combination with suction or blowing devices
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21G—CALENDERS; ACCESSORIES FOR PAPER-MAKING MACHINES
- D21G9/00—Other accessories for paper-making machines
- D21G9/0063—Devices for threading a web tail through a paper-making machine
Definitions
- the present invention relates to a dryer apparatus for drying a pressed web. More specifically, the present invention relates to a dryer apparatus which includes a plurality of single tier dryer sections in which successive sections dry alternate sides of the web as the web is transferred between successive sections without any open draw.
- alternate sides of the web are successively brought into direct contact with the heated surfaces of the drying cylinders as the web moves through the dryer apparatus.
- Such successive drying of alternate sides of the web tends to enhance the uniform drying characteristics of the resultant dried roll.
- vacuum means is used to restrain the web against such cross-machine directional shrinkage and to prevent cross-machine directional shrinkage that would occur in such a transfer if an open draw transfer were utilized.
- DE-U-90 01 209 there is disclosed a dryer apparatus for drying a pressed web according to the preamble of claim 1. More, specifically, DE-U-90 01 209 shows a dryer apparatus comprising a plurality of single tier dryer sections in which successive sections dry alternate sides of the web. The web is transferred between successive sections without any open draw of the web such that the web is uniformly dried on both sides thereof wile the web is restrained against cross-machine directional shrinkage.
- Each of the dryer section includes a single tier of dryers.
- An intermediate roll is disposed between each adjacent dryer of the single tier dryers.
- a dryer felt extends in serpentine configuration around each dryer and intermediate roll such that the web is disposed between the felt and each dryer of the single tier of dryers for drying one side of the web. Also, the felt is disposed in direct contact with an alternate side of the web.
- the dryer apparatus includes a first single tier dryer section for drying one side of the web.
- a second single tier dryer section is disposed immediately downstream relative to the first dryer section for drying an alternate side of the web.
- a transfer means is disposed between the first and second dryer sections for transferring the web without open draw between the first and the second dryer sections.
- the transfer means includes a felt roll which is disposed between the first and the second dryer sections such that the dryer felt extends from the first dryer section to and around the felt roll.
- the felt is disposed between the felt roll and the web.
- a further felt roll is disposed between the felt roll and the first dryer section, and a further felt extends around the further felt roll such that the further felt is disposed between the further felt roll and the web.
- the further felt thereafter extends around the second dryer section so that the web disposed between the felt and the further felt is guided without open draw from the first to the second dryer section.
- Another object of the present invention is the provision of a dryer apparatus including an intermediate roll for diffusing boundary air following a dryer felt that would otherwise tend to lift the web from the felt extending around the intermediate roll.
- Another object of the present invention is the provision of a dryer apparatus having an intermediate roll such that inherent machine directional shrinkage of the web during drying thereof inhibits cross-machine directional shrinkage of the web during movement of the web between successive dryers.
- the intermediate roll defines a plurality of circumferential grooves for diffusing boundary air following the felt that would otherwise tend to lift the web from the felt extending around the intermediate roll, the arrangement being such that inherent machine directional shrinkage of the web during drying thereof inhibits cross-machine directional shrinkage of the web during movement of the web between successive dryers.
- Means are disposed adjacent to the felt roll for urging the web to follow the further felt when the felt and the further felt diverge relative to each other adjacent to the felt roll.
- the means is a blow box disposed on the opposite side of the second felt relative to the web.
- the blow box is connected to a source of pressurized air such that a curtain of air is blown from the blow box onto the further felt so that the web is drawn towards the further felt due to a Coanda effect of the curtain of air relative to the further felt.
- Each of the intermediate rolls has a diameter which is substantially less than the diameter of the adjacent dryers such that the machine directional shrinkage increases the tension of the web between successive dryers.
- the plurality of grooves are spaced in a cross-machine direction along the entire length of the intermediate roll.
- Each groove of the plurality of circumferential grooves extends around the circumference of the intermediate roll so that air pumped into each groove by the dryer felt converging relative to the intermediate roll flows through and around each groove so that a build-up of air pressure at a converging nip defined between the dryer felt and the intermediate roll is inhibited.
- the dryer apparatus includes a vacuum box which is disposed closely adjacent to an unfelted end portion of the intermediate roll.
- the vacuum box is selectively connected to a source of partial vacuum such that in use of the apparatus, during a tail threading operation thereof, the vacuum box is connected to the source of partial vacuum such that air flows in a direction from a tail of the web towards and through the dryer felt and into the circumferential grooves disposed adjacent to the vacuum box and into the vacuum box such that the tail is urged into close conformity with the dryer felt moving around the intermediate roll during the tail threading operation.
- the intermediate roll is a shell roll, the shell defining a plurality of circumferential grooves.
- the shell roll includes a rotatable shell and an internal baffle disposed within the shell.
- the shell and baffle define a tail threading chamber which is disposed adjacent to one end of the intermediate roll.
- Circumferential grooves disposed in the vicinity of the tail threading chamber define aperture means such that the tail threading chamber is disposed in fluid communication with the circumferential grooves disposed in the vicinity of the chamber such that when the tail threading chamber is connected to a source of partial vacuum, air flows from a tail of the web towards and through the dryer felt, through the grooves disposed in the vicinity of the threading chamber, and through the aperture means into the threading chamber so that the tail is urged into close conformity with the dryer felt during a tail threading operation of the dryer apparatus.
- Figure 1 is a side-elevational view of a dryer apparatus generally designated 10 according to the present invention for drying a pressed web W.
- the web W is transferred between successive sections 12, 14 without any open draw of the web W such that the web W is uniformly dried on both sides 16 and 18 thereof while the web W is restrained against cross-machine directional shrinkage.
- Each of the dryer sections 12 and 14 includes a single tier of dryers indicated by the arrow 20 and 22, respectively.
- the dryer section 12 includes a single tier of dryers 24, 25 and 26.
- An intermediate roll 28 is disposed between each adjacent dryer 25 and 25 of the single tier of dryers 20.
- a dryer felt 30 extends in serpentine configuration around each dryer 24 to 26, and intermediate rolls 28 such that the web W is disposed between the felt 30 and each dryer 24 to 26 of the single tier of dryers 20 for drying one side 16 of the web W.
- the intermediate roll 28 defines a plurality of circumferential grooves as shown more clearly in Figure 2 which is a perspective view of one of the intermediate rolls 28.
- the intermediate roll 28 defines a plurality of circumferential grooves 32, 33, 34, 35, 36 and 37 for diffusing boundary air as indicated by the arrows 38 following the felt 30 as shown in Figure 1 that would otherwise tend to lift the web W from the felt 30 extending around the intermediate roll 28.
- the arrangement is such that inherent machine directional shrinkage, as indicated by the arrow MD, during drying thereof inhibits cross-machine directional shrinkage, as indicated by the arrow CD, during movement of the web W between successive dryers 24 and 25.
- the dryer apparatus 10 includes a first single tier dryer section 12 for drying the one side 16 of the web W.
- a second single tier dryer section 14 is disposed immediately downstream relative to the first dryer section 12 for drying the alternate side 18 of the web W.
- the transfer means 40 includes a felt roll 42 which is disposed between the first and second dryer sections 12 and 14 such that the dryer felt 30 extends from the first dryer section 12 to and around the felt roll 42.
- the felt 30 is disposed between the felt roll 42 and the web W.
- a further felt roll 44 is disposed between the felt roll 42 and the first dryer section 12.
- a further felt 46 extends around the further felt roll 44 such that the further felt 46 is disposed between the further felt roll 44 and the web W.
- the further felt 46 thereafter extends around the second dryer section 12 so that the web W disposed between the felt 30 and the further felt 46 is guided without open draw from the first dryer section 12 to the second dryer section 14.
- means 48 is disposed adjacent to the felt roll 42 for urging the web W to follow the further felt 46 when the felt 30 and the further felt 46 diverge relative to each other adjacent to the felt roll 42.
- Figure 2 shows in more detail the intermediate roll 28 which defines a plurality of circumferential grooves 32 to 37.
- the grooves are spaced in a cross-machine direction CD along the entire length of the roll 28.
- each groove of the plurality of grooves 32 to 37 extends around the circumference of the roll 28 so that air 38 pumped into each groove by the dryer felt 30 converging relative to the roll 28 flows through and around each groove so that a build-up of air pressure at a converging nip N defined between the dryer felt 30 and the intermediate roll 28 is inhibited.
- FIG. 3 shows an alternative embodiment of the present invention in which a vacuum box 56 is disposed closely adjacent to an unfelted end portion 58 of the intermediate roll 28.
- the vacuum box 56 is selectively connected to a source of partial vacuum 52A such that in use of the apparatus, during a tail threading operation thereof, the vacuum box 56 is connected to the source of partial vacuum 52A such that air 60 flows in a direction from a tail T of the web W towards and through the dryer felt 30A and into the circumferential groove 32A disposed adjacent to the vacuum box 56 into the vacuum box 56 such that the tail T is urged into close conformity with the dryer felt moving around the intermediate roll 28A during the tail threading operation.
- the intermediate roll 28B is a shell roll with the shell defining a plurality of grooves 32B,33B,34B,35B, and 36B and includes a rotatable shell 62 and an internal baffle 64 disposed within the shell 62.
- the shell 62 and the baffle 64 define a tail threading chamber 66 disposed adjacent to one end 68 of the intermediate roll 28B.
- Circumferential grooves 32B to 36B disposed in the vicinity of the tail threading chamber 66 define aperture means 70 such that the tail threading chamber 66 is disposed in fluid communication with the circumferential grooves 32B to 36B disposed in the vicinity of the chamber 66.
- the arrangement is such that when the tail threading chamber 66 is connected to a source of partial vacuum 52B, air 60B flows from a tail TB of the web web towards and through the dryer felt 30B, through the grooves 32B to 36B disposed in the vicinity of the threading chamber 66, and through the aperture means 70 into the threading chamber 66 so that the tail TB is urged into close conformity with the dryer felt 30B during a tail threading operation of the dryer apparatus.
- machine directional shrinkage of the web as the web dries increases the pressure exerted by the web against the felt during movement of the web and felt around each intermediate roll so that cross-machine directional shrinkage of the web is inhibited throughout the drying operation.
- the present invention overcomes the aforementioned problem by the provision of special felt rolls which replace the aforementioned intermediate vacuum rolls.
- Such special felt rolls require no internal center shaft, internal seals, and extensive drilled through holes which are required in the prior art vacuum rolls.
- these special felt rolls have grooved surfaces to help diffuse boundary layer air which follows the inside surface of the dryer felt.
- the single tier dryer section arrangement according to the present invention is further characterized by having the single tier concept extending beyond the wet end of the dryer section into the dry end portion without the need for the aforementioned costly vacuum rolls.
- One of the novel features of the present invention resides in the recognition that the basic geometry of the single tier dryer section can have a significant and perhaps controlling influence on the shrinkage restraint which is applied to the web, in some cases without the use of an intermediate vacuum roll.
- the web is restrained in the entire apparatus according to U.S. Patent No. 4,934,067 by a combination of felt pressure on the web as it passes over the dryers, and the vacuum restraint applied by the vacuum rolls as the web passes around the vacuum rolls.
- Such combination of restraint mechanism has proven to be effective on lightweight grades at high machine speeds.
- the machine directional shrinkage of the sheet also has an effect on cross-machine directional restraint.
- the web is always supported by a felt, and, therefore, does not experience the stretching effects of external flows of air in open draws of the web and will, accordingly, according to the present invention, actually shrink in a machine direction.
- Such inherent or natural machine directional shrinkage of the web depends on the formation, furnish and fiber orientation but is typically in the range of 2 to 4 percent.
- the sheet length in the dryers at any one time is about 182.88 meters (600 foot).
- the aforementioned 182.88 meters (600 foot) of web has a natural tendency to shrink in the machine direction by 3.66 meters to 7.32 meters (12 to 24 foot).
- Such shrinkage in the range of 3.66 to 7.32 meters (12 to 24 foot) means that the web shrinks on an average between 9.14 and 18.29 centimeters (3.6 to 7.2 inches) between successive dryers if there are 40 dryers in the dryer apparatus.
- the aforementioned shrinkage is largely inhibited by the pressure applied to the web by the tensioned felts as the web wraps the dryer cylinders.
- the web is held both machine directional ends by the dryer felt as it passes over each intermediate roll.
- the increased tendency for the web to shrink in a machine direction then translates into an increase in the machine directional web tension.
- Such web tension then translates into a pressure on the fabric as the web wraps the intermediate roll.
- PS TW/RI kilograms per square centimeter (pounds per square inch), in which TW is the machine directional tension induced by the machine directional shrinkage tendency, and RI is the radius of the intermediate vacuum roll.
- the pressure PS results in a normal force on the felt which, when coupled with the friction between the felt and the web, will prevent or inhibit cross-machine directional shrinkage.
- the effective web tension TW depends on the amount of natural shrinkage that the web exhibits, as well as any plastic relaxation that may occur.
- the total web tension may be further reduced by the centrifugal forces that the web must counter as it passes around the intermediate roll.
- T1 C( B n RI) V 2 /RI, kilograms per linear centimeter (pounds per linear inch), where B is the wet weight of the web expressed in kilograms per square centimeter (pounds per square foot), and V is the velocity of the web expressed in centimeters (feet) per minute, and RI is the radius of the intermediate roll expressed in centimeters (inches).
- n 3.1415
- C is an appropriate conversion factor
- the present invention has particular application to the manufacture of linerboard and other board at speeds less than 914 meters per minute (3,000 feet per minute).
- the present invention provides a no-draw dryer apparatus for uniformly drying both sides of a web which utilizes machine directional shrinkage to inhibit cross-machine directional shrinkage of the resultant web.
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- Drying Of Solid Materials (AREA)
- Paper (AREA)
- Adjustment And Processing Of Grains (AREA)
- Treatment Of Fiber Materials (AREA)
- Orthopedics, Nursing, And Contraception (AREA)
- Medicines Containing Material From Animals Or Micro-Organisms (AREA)
- Diaphragms For Electromechanical Transducers (AREA)
Abstract
Description
- The present invention relates to a dryer apparatus for drying a pressed web. More specifically, the present invention relates to a dryer apparatus which includes a plurality of single tier dryer sections in which successive sections dry alternate sides of the web as the web is transferred between successive sections without any open draw.
- In the papermaking art, a formed web of paper is pressed in a press section in order to remove as much water as possible from the formed web. Subsequently, the pressed web is guided around a plurality of heated drying cylinders in order to remove remaining water from the web.
- Preferably, alternate sides of the web are successively brought into direct contact with the heated surfaces of the drying cylinders as the web moves through the dryer apparatus. Such successive drying of alternate sides of the web tends to enhance the uniform drying characteristics of the resultant dried roll.
- US-A-4,934,067 to Skaugen et al teaches the aforementioned drying apparatus which also permits transfer of the web between successive drying sections without open draw of the web. Consequently, the apparatus disclosed in U.S. Patent No. 4,934,067 enables the restrained drying of the web not only in the wet section of the dryer apparatus, but along the entire length of the dryer apparatus.
- More particularly, because the web is constrained by the dryer felt during transit of the web around the dryer and because vacuum is applied to hold the web on the felt during movement around an intermediate roll, cross-machine directional shrinkage of the web during drying is inhibited.
- Also, during the transfer of the web between successive dryer sections, vacuum means is used to restrain the web against such cross-machine directional shrinkage and to prevent cross-machine directional shrinkage that would occur in such a transfer if an open draw transfer were utilized.
- Therefore, the aforementioned disclosure of US-A-4,934,067 not only enabled enhanced runnability, but also provided improved resultant sheet quality because due to the sheet being restrained against cross-machine directional shrinkage, edge curl of the web was inhibited.
- However, in certain applications, it has been discovered that the provision of intermediate vacuum rolls and the like are unnecessary provided means are supplied for diffusing boundary air following the felt adjacent to such intermediate rolls.
- In DE-U-90 01 209 there is disclosed a dryer apparatus for drying a pressed web according to the preamble of claim 1. More, specifically, DE-U-90 01 209 shows a dryer apparatus comprising a plurality of single tier dryer sections in which successive sections dry alternate sides of the web. The web is transferred between successive sections without any open draw of the web such that the web is uniformly dried on both sides thereof wile the web is restrained against cross-machine directional shrinkage.
- Each of the dryer section includes a single tier of dryers. An intermediate roll is disposed between each adjacent dryer of the single tier dryers. A dryer felt extends in serpentine configuration around each dryer and intermediate roll such that the web is disposed between the felt and each dryer of the single tier of dryers for drying one side of the web. Also, the felt is disposed in direct contact with an alternate side of the web. The dryer apparatus includes a first single tier dryer section for drying one side of the web. A second single tier dryer section is disposed immediately downstream relative to the first dryer section for drying an alternate side of the web.
- A transfer means is disposed between the first and second dryer sections for transferring the web without open draw between the first and the second dryer sections.
- The transfer means includes a felt roll which is disposed between the first and the second dryer sections such that the dryer felt extends from the first dryer section to and around the felt roll. The felt is disposed between the felt roll and the web.
- A further felt roll is disposed between the felt roll and the first dryer section, and a further felt extends around the further felt roll such that the further felt is disposed between the further felt roll and the web. The further felt thereafter extends around the second dryer section so that the web disposed between the felt and the further felt is guided without open draw from the first to the second dryer section.
- A primary disadvantage of the above described prior art configurations as disclosed in DE-U-90 01 209 and in US-A-4,934,067 is the high cost of the intermediate rolls which are vacuum rolls and the need for a vacuum system for such vacuum rolls.
- Therefore, it is a primary objective of the present invention to provide a dryer apparatus which provides a significant contribution to the art of drying a pressed web by overcoming the need for the intermediate roll to be a vacuum roll.
- Another object of the present invention is the provision of a dryer apparatus including an intermediate roll for diffusing boundary air following a dryer felt that would otherwise tend to lift the web from the felt extending around the intermediate roll.
- Another object of the present invention is the provision of a dryer apparatus having an intermediate roll such that inherent machine directional shrinkage of the web during drying thereof inhibits cross-machine directional shrinkage of the web during movement of the web between successive dryers.
- Another object of the present invention is the provision of a dryer apparatus in which each intermediate roll has a diameter which is substantially less than the diameter of adjacent dryers such that the machine directional shrinkage increases the tension of the web between successive dryers so that the pressure exerted by the web against the dryer felt during movement of the web around the intermediate roll is increased in conformity with an equation PS=TW/Rl, where PS is the pressure exerted by the web on the felt, TW is the machine direction tension of the web, and RI is the radius of the intermediate roll.
- Other objects and advantages of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.
- To achieve this, the dryer apparatus of the invention is characterized by the features set forth in the characterizing part of claim 1.
- Specifically, pursuant to the principles of the present invention, the intermediate roll defines a plurality of circumferential grooves for diffusing boundary air following the felt that would otherwise tend to lift the web from the felt extending around the intermediate roll, the arrangement being such that inherent machine directional shrinkage of the web during drying thereof inhibits cross-machine directional shrinkage of the web during movement of the web between successive dryers.
- Means are disposed adjacent to the felt roll for urging the web to follow the further felt when the felt and the further felt diverge relative to each other adjacent to the felt roll.
- In a more specific embodiment of the invention, the means is a blow box disposed on the opposite side of the second felt relative to the web. The blow box is connected to a source of pressurized air such that a curtain of air is blown from the blow box onto the further felt so that the web is drawn towards the further felt due to a Coanda effect of the curtain of air relative to the further felt.
- Each of the intermediate rolls has a diameter which is substantially less than the diameter of the adjacent dryers such that the machine directional shrinkage increases the tension of the web between successive dryers. The arrangement is such that the pressure exerted by the web against the dryer felt during movement of the web around the intermediate roll is increased in conformity with the equation PS = TW/RI kilograms per square centimeter (pounds per square inch), where PS is the pressure exerted by the web on the dryer felt extending around the intermediate roll, TW is the machine direction tension of the web induced by the machine directional shrinkage of the web during drying, and RI is the radius of the intermediate roll.
- In a preferred embodiment of the present invention, the plurality of grooves are spaced in a cross-machine direction along the entire length of the intermediate roll.
- Each groove of the plurality of circumferential grooves extends around the circumference of the intermediate roll so that air pumped into each groove by the dryer felt converging relative to the intermediate roll flows through and around each groove so that a build-up of air pressure at a converging nip defined between the dryer felt and the intermediate roll is inhibited.
- In an alternative embodiment of the present invention, the dryer apparatus includes a vacuum box which is disposed closely adjacent to an unfelted end portion of the intermediate roll. The vacuum box is selectively connected to a source of partial vacuum such that in use of the apparatus, during a tail threading operation thereof, the vacuum box is connected to the source of partial vacuum such that air flows in a direction from a tail of the web towards and through the dryer felt and into the circumferential grooves disposed adjacent to the vacuum box and into the vacuum box such that the tail is urged into close conformity with the dryer felt moving around the intermediate roll during the tail threading operation.
- In one embodiment of the present invention, the intermediate roll is a shell roll, the shell defining a plurality of circumferential grooves.
- More specifically, the shell roll includes a rotatable shell and an internal baffle disposed within the shell. The shell and baffle define a tail threading chamber which is disposed adjacent to one end of the intermediate roll.
- Circumferential grooves disposed in the vicinity of the tail threading chamber define aperture means such that the tail threading chamber is disposed in fluid communication with the circumferential grooves disposed in the vicinity of the chamber such that when the tail threading chamber is connected to a source of partial vacuum, air flows from a tail of the web towards and through the dryer felt, through the grooves disposed in the vicinity of the threading chamber, and through the aperture means into the threading chamber so that the tail is urged into close conformity with the dryer felt during a tail threading operation of the dryer apparatus.
- Many modifications and variations of the present invention will be readily apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings. However, such modifications and variations fall within the spirit and scope of the present invention as defined by the appended claims.
-
- Figure 1 is a side-elevational view of a dryer apparatus according to the present invention;
- Figure 2 is a perspective view of an intermediate roll according to the present invention showing a plurality of circumferential grooves defined thereby;
- Figure 3 is a fragmentary sectional view of one embodiment of the present invention showing a portion of an intermediate roll together with an adjacent vacuum box; and
- Figure 4 is a fragmentary sectional view of an alternate embodiment of the present invention showing an intermediate roll including a shell and a baffle defining a tail threading chamber.
- Similar reference characters refer to similar parts throughout the various embodiments of the present invention.
- Figure 1 is a side-elevational view of a dryer apparatus generally designated 10 according to the present invention for drying a pressed web W.
- The
dryer apparatus 10 includes a plurality of singletier dryer sections successive sections alternate sides - The web W is transferred between
successive sections sides - Each of the
dryer sections arrow 20 and 22, respectively. - More specifically, the
dryer section 12 includes a single tier ofdryers - An
intermediate roll 28 is disposed between eachadjacent dryer dryers 20. - A dryer felt 30 extends in serpentine configuration around each
dryer 24 to 26, andintermediate rolls 28 such that the web W is disposed between thefelt 30 and eachdryer 24 to 26 of the single tier ofdryers 20 for drying oneside 16 of the web W. - The felt 30 is also disposed between the
intermediate roll 28 and the web W so that thefelt 30 is disposed in direct contact with analternate side 18 of the web W. - The
intermediate roll 28 defines a plurality of circumferential grooves as shown more clearly in Figure 2 which is a perspective view of one of the intermediate rolls 28. - As shown in Figure 2, the
intermediate roll 28 defines a plurality ofcircumferential grooves arrows 38 following the felt 30 as shown in Figure 1 that would otherwise tend to lift the web W from the felt 30 extending around theintermediate roll 28. - The arrangement is such that inherent machine directional shrinkage, as indicated by the arrow MD, during drying thereof inhibits cross-machine directional shrinkage, as indicated by the arrow CD, during movement of the web W between
successive dryers - More specifically, with reference to Figure 1, the
dryer apparatus 10 includes a first singletier dryer section 12 for drying the oneside 16 of the web W. - A second single
tier dryer section 14 is disposed immediately downstream relative to thefirst dryer section 12 for drying thealternate side 18 of the web W. - Transfer means generally designated 40 is disposed between the first and the
second dryer sections second dryer sections - More specifically, the transfer means 40 includes a felt
roll 42 which is disposed between the first andsecond dryer sections first dryer section 12 to and around the feltroll 42. The felt 30 is disposed between the feltroll 42 and the web W. - A further felt
roll 44 is disposed between the feltroll 42 and thefirst dryer section 12. - Also, a further felt 46 extends around the further felt
roll 44 such that the further felt 46 is disposed between thefurther felt roll 44 and the web W. The further felt 46 thereafter extends around thesecond dryer section 12 so that the web W disposed between the felt 30 and the further felt 46 is guided without open draw from thefirst dryer section 12 to thesecond dryer section 14. - More particularly, as shown in Figure 1, means 48 is disposed adjacent to the felt
roll 42 for urging the web W to follow the further felt 46 when the felt 30 and the further felt 46 diverge relative to each other adjacent to the feltroll 42. - As shown in Figure 1, the
means 48 is ablow box 50 which is disposed on the opposite side of the further felt 46 relative to the web W. Theblow box 50 is connected to a source ofpressurized air 52 such that a curtain of air, indicated by the arrow 54, is blown from theblow box 50 onto the further felt 46 so that the web W is drawn towards the further felt 46 due to a Coanda effect of the curtain of air 54 relative to the further felt 46. - As clearly shown in Figure 1, each of the
intermediate rolls 28 has a diameter d which is substantially less than the diameter D ofadjacent dryers 24 to 26 such that the machine directional shrinkage MD increases the tension of the web W betweensuccessive dryers intermediate roll 28 is increased in conformity with the equation PS = TW/Rl kilograms per square centimeter (pounds per square inch), where PS is the pressure exerted by the web W on the dryer felt 30 extending around theintermediate roll 28, TW is the machine direction tension of the web W induced by the machine directional shrinkage of the web W during drying, and RI is the radius of theintermediate roll 28. - Figure 2 shows in more detail the
intermediate roll 28 which defines a plurality ofcircumferential grooves 32 to 37. The grooves are spaced in a cross-machine direction CD along the entire length of theroll 28. - As shown in Figure 2, each groove of the plurality of
grooves 32 to 37 extends around the circumference of theroll 28 so thatair 38 pumped into each groove by the dryer felt 30 converging relative to theroll 28 flows through and around each groove so that a build-up of air pressure at a converging nip N defined between the dryer felt 30 and theintermediate roll 28 is inhibited. - Figure 3 shows an alternative embodiment of the present invention in which a
vacuum box 56 is disposed closely adjacent to anunfelted end portion 58 of theintermediate roll 28. Thevacuum box 56 is selectively connected to a source ofpartial vacuum 52A such that in use of the apparatus, during a tail threading operation thereof, thevacuum box 56 is connected to the source ofpartial vacuum 52A such thatair 60 flows in a direction from a tail T of the web W towards and through the dryer felt 30A and into thecircumferential groove 32A disposed adjacent to thevacuum box 56 into thevacuum box 56 such that the tail T is urged into close conformity with the dryer felt moving around theintermediate roll 28A during the tail threading operation. - In an alternative embodiment of the present invention, the
intermediate roll 28B is a shell roll with the shell defining a plurality ofgrooves rotatable shell 62 and aninternal baffle 64 disposed within theshell 62. Theshell 62 and thebaffle 64 define atail threading chamber 66 disposed adjacent to oneend 68 of theintermediate roll 28B. -
Circumferential grooves 32B to 36B disposed in the vicinity of thetail threading chamber 66 define aperture means 70 such that thetail threading chamber 66 is disposed in fluid communication with thecircumferential grooves 32B to 36B disposed in the vicinity of thechamber 66. - The arrangement is such that when the
tail threading chamber 66 is connected to a source ofpartial vacuum 52B,air 60B flows from a tail TB of the web web towards and through the dryer felt 30B, through thegrooves 32B to 36B disposed in the vicinity of the threadingchamber 66, and through the aperture means 70 into the threadingchamber 66 so that the tail TB is urged into close conformity with the dryer felt 30B during a tail threading operation of the dryer apparatus. - In operation of the apparatus according to the present invention, machine directional shrinkage of the web as the web dries increases the pressure exerted by the web against the felt during movement of the web and felt around each intermediate roll so that cross-machine directional shrinkage of the web is inhibited throughout the drying operation.
- More specifically, in the prior art single tier dryer sections, special vacuum rolls are utilized to improve sheet runnability and sheet restraint and in some cases to provide the ability to thread the dryer section without the use of rope threading devices.
- Such prior art configurations, as disclosed in U.S. Patent No. 4,934,067, have been shown commercially to be an effective design to achieve the aforementioned objectives.
- However, a primary disadvantage of the aforementioned design of U.S. Patent No. 4,934,067 is the high cost of vacuum rolls and the need for a vacuum system for such rolls.
- The present invention overcomes the aforementioned problem by the provision of special felt rolls which replace the aforementioned intermediate vacuum rolls. Such special felt rolls require no internal center shaft, internal seals, and extensive drilled through holes which are required in the prior art vacuum rolls. Specifically, these special felt rolls have grooved surfaces to help diffuse boundary layer air which follows the inside surface of the dryer felt. The single tier dryer section arrangement according to the present invention is further characterized by having the single tier concept extending beyond the wet end of the dryer section into the dry end portion without the need for the aforementioned costly vacuum rolls.
- One of the novel features of the present invention resides in the recognition that the basic geometry of the single tier dryer section can have a significant and perhaps controlling influence on the shrinkage restraint which is applied to the web, in some cases without the use of an intermediate vacuum roll.
- The following includes an analysis which highlights the essential features of the inventive concept according to the present invention.
- The web is restrained in the entire apparatus according to U.S. Patent No. 4,934,067 by a combination of felt pressure on the web as it passes over the dryers, and the vacuum restraint applied by the vacuum rolls as the web passes around the vacuum rolls. Such combination of restraint mechanism has proven to be effective on lightweight grades at high machine speeds.
- The frictional contact developed between the web and the felt and dryer in the first case and between the web and the felt in the second case inhibits the web from contracting in the cross-machine direction. Such is distinctly different from the more common two-tier dryer section arrangements in which the web experiences very little cross-machine directional restraint in the open draws between dryer cylinders.
- In the first case, the pressure applied to the web is given by the equation P1 = T/RD kilograms per square centimeter (pounds per square inch), in which T represents the effective tension in the felt in kilograms per linear centimeter (pounds per linear inch), and RD represents the radius of the dryer cylinder in centimeters (inches).
- In the second case, the pressure applied to the web is given by the equation P2 = PV kilograms per square centimeter (pounds per square inch), in which PV is the vacuum inside the vacuum roll expressed in kilograms per square centimeter (pounds per square inch).
- The above analysis describes the restraint mechanisms which have been recognized to be operative in the dryer sections according to U.S. Patent No. 4,934,067 and the various modifications thereof.
- However, it has been discovered that the machine directional shrinkage of the sheet also has an effect on cross-machine directional restraint. In the single tier geometry of the present invention, the web is always supported by a felt, and, therefore, does not experience the stretching effects of external flows of air in open draws of the web and will, accordingly, according to the present invention, actually shrink in a machine direction.
- Such inherent or natural machine directional shrinkage of the web depends on the formation, furnish and fiber orientation but is typically in the range of 2 to 4 percent. In a typical dryer section with 40 dryers, the sheet length in the dryers at any one time is about 182.88 meters (600 foot). The aforementioned 182.88 meters (600 foot) of web has a natural tendency to shrink in the machine direction by 3.66 meters to 7.32 meters (12 to 24 foot). Such shrinkage in the range of 3.66 to 7.32 meters (12 to 24 foot) means that the web shrinks on an average between 9.14 and 18.29 centimeters (3.6 to 7.2 inches) between successive dryers if there are 40 dryers in the dryer apparatus. The aforementioned shrinkage is largely inhibited by the pressure applied to the web by the tensioned felts as the web wraps the dryer cylinders.
- Effectively, the web is held both machine directional ends by the dryer felt as it passes over each intermediate roll. The increased tendency for the web to shrink in a machine direction then translates into an increase in the machine directional web tension. Such web tension then translates into a pressure on the fabric as the web wraps the intermediate roll. Such pressure is given by the equation PS = TW/RI kilograms per square centimeter (pounds per square inch), in which TW is the machine directional tension induced by the machine directional shrinkage tendency, and RI is the radius of the intermediate vacuum roll.
- The pressure PS results in a normal force on the felt which, when coupled with the friction between the felt and the web, will prevent or inhibit cross-machine directional shrinkage.
- IT has been further noted that the effective web tension TW depends on the amount of natural shrinkage that the web exhibits, as well as any plastic relaxation that may occur. The total web tension may be further reduced by the centrifugal forces that the web must counter as it passes around the intermediate roll.
- If DL represents the shrinkage tendency of the web in centimeters (inches), and "e" represents the amount of relaxation of the web, expressed in centimeters (inches), and if "E" represents the effective modulus of the web, expressed in kilograms per square centimeter (pounds per square inch), then the total tension developed in the web between cylinders would be Tt = (DL - e) E, kilograms per linear centimeter (pounds per linear inch).
- The loss in effective tension as applied by the web to the dryer felt due to centrifugal forces can be approximated.
- More specifically, for intermediate rolls that have a wrap angle of 180 degrees, the aforementioned approximation is represented by the equation T1 = C(B n RI) V2/RI, kilograms per linear centimeter (pounds per linear inch), where B is the wet weight of the web expressed in kilograms per square centimeter (pounds per square foot), and V is the velocity of the web expressed in centimeters (feet) per minute, and RI is the radius of the intermediate roll expressed in centimeters (inches).
- It is to be noted that n equals 3.1415, and that C is an appropriate conversion factor.
- Consequently, it has been noted that the loss in tension due to the centrifugal force does not depend on the radius of the intermediate roll.
- From the above and by combining the above equations, an expression for the pressure applied by the web to the fabric is:
- PS = TW /RI
- PS = (Tt-T1)/R!
- PS = ((DL - e) E - C(B n V2)) / RI, kilograms per linear centimeter (pli)
- From the aforementioned equation, it was discovered that the natural tendency of the web to shrink in a machine direction can be utilized for inhibiting cross-machine directional shrinkage by generating pressure on the dryer felt, and that this inhibition of cross-machine directional shrinkage will be larger for the following conditions:
- 1) Small diameter intermediate roll (small RI)
- 2) Low speed machines (low V)
- 3) Minimum web relaxation (small e)
- 4) High wet web modulus (high E)
- 5) High natural machine directional shrinkage rates (high (DL)
- It has also been observed that the relaxation of the web stress (e) is a time related phenomenon. In other words, there will be less relaxation if the time is short. For a given machine speed, such will be achieved with a small diameter intermediate roll, with short felt tangent lengths between the dryers and associated intermediate rolls.
- Accordingly, the present invention has particular application to the manufacture of linerboard and other board at speeds less than 914 meters per minute (3,000 feet per minute).
- The present invention provides a no-draw dryer apparatus for uniformly drying both sides of a web which utilizes machine directional shrinkage to inhibit cross-machine directional shrinkage of the resultant web.
Claims (8)
characterized in that said intermediate roll (28) defines a plurality of circumferential grooves (32,33,34,35,36,37) for diffusing boundary air (38) following said felt (30) that would otherwise tend to lift the web (W) from said felt (30) extending around said intermediate roll (28), the arrangement being such that inherent machine directional shrinkage (MD) of the web (W) during drying thereof inhibits cross-machine directional shrinkage (CD) of the web (W) during movement of the web (W) between successive dryers (24,25),
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/606,654 US5241760A (en) | 1987-02-13 | 1990-10-31 | Dryer apparatus |
PCT/US1991/007062 WO1992008004A1 (en) | 1990-10-31 | 1991-09-26 | Dryer apparatus |
US606654 | 2000-06-28 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0555334A1 EP0555334A1 (en) | 1993-08-18 |
EP0555334B1 true EP0555334B1 (en) | 1995-02-22 |
EP0555334B2 EP0555334B2 (en) | 1998-08-26 |
Family
ID=24428897
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP91920008A Expired - Lifetime EP0555334B2 (en) | 1990-10-31 | 1991-09-26 | Dryer apparatus |
Country Status (12)
Country | Link |
---|---|
US (1) | US5241760A (en) |
EP (1) | EP0555334B2 (en) |
JP (1) | JP2553429B2 (en) |
KR (1) | KR100191141B1 (en) |
AT (1) | ATE118844T1 (en) |
AU (1) | AU654158B2 (en) |
BR (1) | BR9107035A (en) |
CA (1) | CA2093792C (en) |
DE (2) | DE555334T1 (en) |
ES (1) | ES2042478T5 (en) |
FI (1) | FI931948A0 (en) |
WO (1) | WO1992008004A1 (en) |
Families Citing this family (14)
Publication number | Priority date | Publication date | Assignee | Title |
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US5404653A (en) | 1987-02-13 | 1995-04-11 | Beloit Technologies, Inc. | Apparatus for drying a web |
FI95491C (en) * | 1992-12-30 | 1996-02-12 | Valmet Paper Machinery Inc | Paper machine drying section |
US5553392A (en) * | 1993-11-15 | 1996-09-10 | Tokushu Paper Mfg. Co., Ltd. | Process and apparatus for drying sheet materials |
US5579589A (en) * | 1995-05-15 | 1996-12-03 | Voith Sulzer Papermaschinen Gmbh | Process and apparatus for drying a fibrous web in a single-felt dryer group under low vacuum |
US5535527A (en) * | 1995-06-07 | 1996-07-16 | Valmet Corporation | Method and arrangement in a multi-cylinder dryer of a paper machine |
DE19615227A1 (en) * | 1996-04-18 | 1997-10-23 | Voith Sulzer Papiermasch Gmbh | Machine for the production of a material web |
FI114932B (en) * | 1997-12-18 | 2005-01-31 | Metso Paper Inc | Method and apparatus for optimizing drying of a paper web |
DE20020772U1 (en) * | 2000-12-07 | 2002-04-18 | BrĂĽckner Maschinenbau GmbH, 83313 Siegsdorf | suction roll |
US7001487B2 (en) * | 2001-12-19 | 2006-02-21 | Kimberly-Clark Worldwide, Inc. | Method and apparatus for transporting a sheet from a dryer to a reel |
US6904700B2 (en) * | 2003-09-12 | 2005-06-14 | Kimberly-Clark Worldwide, Inc. | Apparatus for drying a tissue web |
US7721464B2 (en) | 2003-09-12 | 2010-05-25 | Kimberly-Clark Worldwide, Inc. | System and process for throughdrying tissue products |
FI118999B (en) * | 2003-10-07 | 2008-06-13 | Metso Paper Inc | Paper or board machine roller and paper or board machine drying group |
US6877246B1 (en) * | 2003-12-30 | 2005-04-12 | Kimberly-Clark Worldwide, Inc. | Through-air dryer assembly |
US20070193057A1 (en) * | 2006-01-26 | 2007-08-23 | Girolamo Paul A | Rotatable vacuum transfer roll apparatus |
Family Cites Families (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3250019A (en) * | 1962-09-10 | 1966-05-10 | Edward D Beachler | Dryer felt |
DE2212209C3 (en) * | 1972-03-14 | 1980-05-29 | Escher Wyss Gmbh, 7980 Ravensburg | Dryer section |
FI53333C (en) * | 1972-11-13 | 1978-04-10 | Valmet Oy | TORKNINGSCYLINDERGRUPP I EN FLERCYLINDERTORK FOER EN MATERIALBANA I SYNNERHET FOER PAPPER |
US3874997A (en) * | 1973-03-21 | 1975-04-01 | Valmet Oy | Multiple cylinder drier in a paper machine |
JPS5464111A (en) * | 1977-10-24 | 1979-05-23 | Japan Steel Works Ltd | Suction roll for paper making |
US4359827B1 (en) * | 1979-11-05 | 1994-03-29 | Keith V Thomas | High speed paper drying |
JPS6029800A (en) * | 1983-07-29 | 1985-02-15 | ć ŞĺĽŹäĽšç¤ľćť±čŠť | Voice analysis system |
JPS6123319A (en) * | 1984-07-12 | 1986-01-31 | Canon Inc | Observation apparatus |
CA1250744A (en) * | 1984-12-20 | 1989-03-07 | Ralph J. Futcher | Drier felting arrangement |
FI76142C (en) * | 1985-11-14 | 1988-09-09 | Valmet Oy | FICKVENTILATIONSFOERFARANDE OCH -ANORDNING I EN PAPPERSMASKINS MAONGCYLINDERTORK. |
US4698919A (en) * | 1986-04-08 | 1987-10-13 | Beloit Corp. | Apparatus for assisting the transfer of a web to a drying section |
ATE50303T1 (en) * | 1986-04-08 | 1990-02-15 | Beloit Corp | BLOW BOX FOR DRYER. |
JPS6389996U (en) * | 1986-12-02 | 1988-06-10 | ||
US4934067A (en) * | 1987-02-13 | 1990-06-19 | Beloit Corporation | Apparatus for drying a web |
US5101577A (en) * | 1987-02-13 | 1992-04-07 | Beloit Corporation | Web transfer apparatus |
US4882854A (en) * | 1987-05-26 | 1989-11-28 | Beloit Corporation | Guide roll apparatus for a dryer of a paper machine drying section |
FI83680C (en) * | 1988-03-09 | 1991-08-12 | Valmet Paper Machinery Inc | FOERFARANDE OCH ANORDNING VID DRAGNINGEN AV BANAN I EN PAPPERSMASKIN SAMT CYLINDER FOER ANVAENDNING VID DRAGNINGEN AV BANAN. |
US4891891A (en) * | 1988-10-11 | 1990-01-09 | Beloit Corporation | Dryer section apparatus and method |
FI97245C (en) * | 1989-12-12 | 1996-11-11 | Valmet Paper Machinery Inc | Suction drum for paper machine |
DE9001209U1 (en) * | 1990-02-03 | 1990-04-05 | J.M. Voith Gmbh, 7920 Heidenheim | Dry section |
-
1990
- 1990-10-31 US US07/606,654 patent/US5241760A/en not_active Expired - Lifetime
-
1991
- 1991-09-26 AU AU89093/91A patent/AU654158B2/en not_active Ceased
- 1991-09-26 JP JP3518343A patent/JP2553429B2/en not_active Expired - Fee Related
- 1991-09-26 DE DE91920008T patent/DE555334T1/en active Pending
- 1991-09-26 ES ES91920008T patent/ES2042478T5/en not_active Expired - Lifetime
- 1991-09-26 CA CA002093792A patent/CA2093792C/en not_active Expired - Fee Related
- 1991-09-26 EP EP91920008A patent/EP0555334B2/en not_active Expired - Lifetime
- 1991-09-26 AT AT91920008T patent/ATE118844T1/en not_active IP Right Cessation
- 1991-09-26 KR KR1019930701298A patent/KR100191141B1/en not_active IP Right Cessation
- 1991-09-26 WO PCT/US1991/007062 patent/WO1992008004A1/en active IP Right Grant
- 1991-09-26 DE DE69107625T patent/DE69107625T3/en not_active Expired - Fee Related
- 1991-09-26 BR BR919107035A patent/BR9107035A/en not_active IP Right Cessation
-
1993
- 1993-04-29 FI FI931948A patent/FI931948A0/en unknown
Also Published As
Publication number | Publication date |
---|---|
ES2042478T3 (en) | 1995-06-16 |
KR930702583A (en) | 1993-09-09 |
ES2042478T1 (en) | 1993-12-16 |
BR9107035A (en) | 1993-09-08 |
DE69107625T3 (en) | 1998-12-03 |
JPH05506281A (en) | 1993-09-16 |
WO1992008004A1 (en) | 1992-05-14 |
ES2042478T5 (en) | 1998-12-16 |
FI931948A (en) | 1993-04-29 |
AU8909391A (en) | 1992-05-26 |
AU654158B2 (en) | 1994-10-27 |
ATE118844T1 (en) | 1995-03-15 |
CA2093792C (en) | 1996-10-01 |
DE555334T1 (en) | 1994-02-03 |
EP0555334A1 (en) | 1993-08-18 |
US5241760A (en) | 1993-09-07 |
KR100191141B1 (en) | 1999-06-15 |
DE69107625D1 (en) | 1995-03-30 |
CA2093792A1 (en) | 1992-05-01 |
EP0555334B2 (en) | 1998-08-26 |
JP2553429B2 (en) | 1996-11-13 |
DE69107625T2 (en) | 1995-07-27 |
FI931948A0 (en) | 1993-04-29 |
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